Utilization of Plankton in Science Education

Abstract

The active bodies and the resistance cysts of Blepharisma undulans japonicus Suzuki, 1954〔B. japonicum Suzuki (Bhandary, A. V. 1962), Plankton, Ciliata〕were cultured under the definite condition, and the following valuable results in science education 〔(1), (2)〕wereobtained. (1) As the teaching materials, the active bodies and the resistance cysts of the AR strain of this subspecies were more suitable than those of Paramecium etc., due to the following points of (a) and (b). (a) The active bodies are easily cultivable like those of Paramecium etc. by the rice straw infusion (Fig. 1, Fig. 2, Table 1). They are beautifully reddish in color, very large in size (about 650μ,～730μ, in length, about 230μ,～300μ, in width), and seen by the naked eyes. They move forward, smoothly and very slowly (3sec.～8sec./mm.). Therefore, an active body in the culture medium is easily taken by a pipette, and its descendants are easily reproduced numerously by the repeated binary divisions (Table 2). Moreover, the resistance cysts are brownish black in color, roundish or ovoid (about 90μ,～170μ, in long dia., about 80μ,～140μ, in short dia.), and able to be kept living in the culture medium for a long period and germinated at need (Table 3, Fig. 3). (b) Such a curriculum as the individuals of this strain are used as the teaching materials instead of Paramecium etc., was applied to the pupils of the kindergartens, elementary schools, junior high schools and senior high schools. It was confirmed that the educational value of such a curriculum was higher than that of the traditional one which used Paramecium etc., (refer to 〔5〕）．(2) The following important points (a)～(g) which have not been studied yet were investigated, by cultivating the following (1)～(5) strains of this subspecies under the definite condition (the rice straw infusion, 25°±1°C, pH 7.0±0.2, etc,) ; (1) the red active bodies of the AR strain, (2) the white active bodies of the AW strain which are the variations of the red active bodies of the AR strain without passing through the stage of the resistance cyst, (3) the red active bodies of the BR strain, (4) those of the CR strain and (5) those of the DR strain. (a) The topographical habitat of this sub species and the average chemical composition of the water in the habitat (Fig. 1, Photo graph 9, Table 1). (b) The biotope of the individuals of the AR strain concerning a change of temperature or pH of the culture medium, and especially the range of the formation of the resistance cysts of this strain (Fig. 2). (c) The days required for the excystments of the resistance cysts of the AR strain increase according as the days after their formations increase. The ratios of their excystments are also researched (Table 3). (d) The active bodies of both the AR strain and the AW strain possess negative geotaxis, which is almost of the same grade in both strains (Table 4). (e) The active bodies of both the AR strain and the AW strain possess negative phototaxis, which is almost of the same grade in both strains (Table 5). (f) The active bodies of both the AR strain and the AW strain possess negative electrotaxis, which is a little more con spicuous in the latter than in the former (Table 6). (g) The mating experiments among four strains, i. e., AR, BR, CR, and DR strains (Table 7). On the basis of these points (a)～(g), we conclude that the exploitation of this sub species as the teaching materials is very effective in science education.